We are replacing a 2.5 ton air handler in the attic above garage. Unit will be located 30-35 ft from the 'closest air conditioned room'. The farthest room receiving air is 50 ft from the air handler.
Question is - contractors want to run flex pipe from new unit to existing return and supply connections (30 ft run) using 12" diam. flex. I think the pressure loss will be high and that air flow would be better with larger diam. flex (16" or 18"). contractor disagrees but i think he wants to spend less by using smaller ducting.
Any advice on this?